The invention relates to a semiconductor device. More specifically, the invention relates to a method for forming an isolation layer in a semiconductor device capable of improving gap-fill margin upon deposition of an isolation layer.
In recent trends toward high-integration and fine-pattern semiconductor devices, there has been increased importance for shallow trench isolation (STI) techniques that exhibit superior device isolation performance with small width Formation of an isolation layer with a shallow trench isolation technique is generally carried out by forming a trench inside a semiconductor substrate, filling the trench with an insulating layer, and subjecting the resulting structure to planarization.
In forming the insulating layer for filling the trench, repetition of deposition-etching-deposition (DED) is used to improve gap-fill performance. During the repeated process, overhangs that results from the deposition of the insulating layer inside the trench having a small width, can be removed by etching. However, there is a limitation in applying the method for repeating deposition-etching-deposition to a trench having a low gap-fill margin due to the reduced size thereof.
FIGS. 1 and 2 are views illustrating defects resulted from formation of an isolation layer in a semiconductor device.
As shown in FIGS. 1 and 2, during etching used to remove overhangs occurring upon deposition of an insulating layer for filling the trench, the insulating layer undergoes surface-variation into a porous oxide layer. The porous oxide layer undergoes lifting and leave a lift defect A on the surface of a semiconductor substrate in the subsequent planarization and cleaning. Meanwhile, the surface of the insulating layer is attacked by a wet chemical for use in wet etching to remove the overhangs. As a result, a lift defect occurs, that is, the insulating layer is partially detached due to weaken binding force between the insulating layer and an oxide layer deposited in the following process.
As shown in FIG. 2, the lift defect A remaining on a wafer spreads over the overall wafer, thus causing a deterioration in the characteristics of the semiconductor substrate.